Wireless communication services are available to wireless User Equipment (UE) over Long Term Evolution (LTE) networks. In the LTE networks, the UEs wirelessly attach to eNodeBs which are supported by Mobility Management Entities (MMEs). During the attachment process, the MMEs send their Radio Access Technology Frequency Selection Priority (RFSP) indices to the eNodeBs.
The eNodeBs translate these RFSP indices into frequency selection priorities for the UEs. The eNodeBs transfer the frequency selection priorities to the UEs. The UEs process the frequency selection priorities to select their communication frequencies. Typically, a given frequency selection priority comprises an ordered list of frequencies and correlated selection parameters, such as signal strength thresholds, signal-to-noise ratios, hysteresis timers, and the like. The UEs and the eNodeBs communicate over the communication frequencies selected by the UEs based on the frequency selection priorities.
Eventually, the UEs enter the idle mode. In the idle mode, the UEs may periodically read signaling and send status, but the idle UEs do not exchange user data. During idle mode entry, the eNodeBs identify Voice over LTE (VoLTE) users by their Subscriber Profile Identifiers (SPIDs). The eNodeBs send connection release messages instructing the VoLTE UEs to idle using a different frequency selection priority for a time period before reverting to their initial frequency selection priorities.
During idle mode, the VoLTE UEs use the different frequency selection priority to select their communication frequencies for the time period. Thus, the selected communication frequencies may vary during the time period. When the time period expires, the VoLTE UEs again use the initial frequency selection priority to select their communication frequencies. If the eNodeBs receive data messages for idling UEs, then the eNodeBs transfer the messages over the initial communication frequencies. Unfortunately, some of the VoLTE UEs may be idling on a different frequency and miss the message until the data message is resent over a wider range of frequencies.